CDMA Mobiles - Why not with SIM?

'cause GSM standard people was smarter and CDMA standard used in TDMA US environment didn't provide it.

For your second question - CDMA concept does not prevent the use of SIM-like card.

Seeampapa,

I dunno what service provider you are talking of as initially mine one too provided connection without a SIM but now I have the same number with a SIM.

Suggest,, leave your computer and go check up the service provider and stop putting these kind of questions in this forum that can be sorted out at your end itself.

Well, you got a couple of good answers, but let me provide a bit more information.

There is nothing in CDMA that prevents or requires a SIM card. Basically, a SIM card is the "brains" of the cell phone, containing information to identify the subscriber to the network for access and services. That explains its name: Subscriber Identity Module. In GSM, where SIM cards originated, the card also contains the phone book or contact list.

Depending on where you are in the world, the SIM card may be locked or unlicked. Unlocked cards can be used in any device. Locked cards can only be used in one particular device. This is because the service providers in those countries subsidize the purchase price of the device. Therefore, they don't want to lose you (and the money) to a competitor. By the time CDMA came along, the devices were expensive enough, and subsidized enough that there was no reason to build devices with removable SIM cards. Since it was going to be locked anyway, just burn the info into memory on the chipset and be done with it. But, even with that, there is nothing that prevents a manufacturer from creating SIM card capable CDMA devices.

As to your second question, the orthogonal codes have nothing to do with the services provided. The codes, known as Walsh Codes (there are 64 of them) are used in CDMA to identify traffic. The codes are used to encode traffic to and from a particular handset or device. By assigning a particular code, both the tower and the device can identify traffic from the device or to it. This way, multiple handsets can talk to a tower simultaneously on a single frequency range. Certain codes are reserved: Code 0 for the pilot channel, 32 for the synch channel, 1-6 for paging channels, and the remainder for traffic channels.

There is actually quite a bit more that goes on in CDMA transmissions, but that it the basic use of the Walsh Code.